Ice_Wolf

Well, now that I know for sure that I want to start with a turbo car when I build up a RX-7, I'm wondering what all the differences were between the years. I know of the usually differences between the S4 and S5 models like the bumpers, trim, tailights, mirrors, wing, rims, engine, and interior. The S5 had the better plastics on the interior that didn't crack as easily, and had the nicer seats and door panels, along with different style gauges, idiot light setup, logicon, and the optional cargo cover. The engine had the same irons and housings, but had stronger internals allowing it to rev higher and higher compression rotors as well as a different turbo. I don't remember if the intake and exhaust manifolds were setup the same though. Also, I believe the tranny was different, but the driveshaft, differential, and axles were the same. I do remember some people saying the S4 had a stronger drivetrain though, wasn't sure if there was any truth to this. IIRC, the 87-88 TII had the "heavy duty" suspension, whereas the other years just had the regular TII suspension setup. All TII's had the same brakes though IIRC. Anything to add to this to aid in my finding a TII?

Jpk3200

Twin scroll turbo system and electronically-controlled waste gate. Sounds like you already know most of the differences.

13b4me

S4 TII has different manifolds, and different turbo/mani. It also has a 7.62 5th gear, while the S5 has a 7.19 5th gear. S4's have a clutch type LSD, and S5's have a viscous. Suspension was the same for all models.

Jpk3200

Almost forgot, but I believe that the CPU speed was doubled and that the AFM was changed to linear-type from flapper. The s5 had a larger gas tank (18.5 gallons).

Ice_Wolf

Yea, I knew about the twin-scroll system and the electronically controlled wastegate. I never knew the manifolds were different, but I did know the turbo was different because of the twin-scroll system. I didn't know that about the 5th gear on the tranny though. Basically, the 5th gear on the S5 will save you more gas mileage because it'll run at a lower RPM, but if you're looking for acceleration, the S4 is going to be better in 5th gear. The tranny thing isn't a big deal considering this car will be built for speed, not gas mileage. I forgot about the different rear-end types, but I knew the viscous type differential was better. I was told the 87-88 had the "heavy duty" suspension, but the other TII's had the standard TII suspension by Ice Mark. Never knew that about the CPU speed, but I did hear about the changes with the AFM. The gas tank thing isn't a big issue either, considering I only fill half full to get better gas mileage anyways. Now, how many of these parts are swappable? I'm sure the rear-ends are swappable. Could I put the better turbo and manifold setups on a S4? What about swapping the CPU and AFM?

13b4me

It's debatable whether the viscous LSD is better. I personally prefer the clutch type LSD, because the transition is more predictable. You can run S5 intake manifolds on your S4, as well as the S5 turbo and manifold. The S5 turbo also has a better wastegate design. All TII suspension is the same, as well as the 86-87 Sport, 88 GTU, and 89-90 GTUs.

Here's a diagram for the AFM swap.

Ice_Wolf

What do you mean by the clutch type being more predictable? That's good to hear the intake manifolds, exhaust manifold, and turbo are all direct swaps from S5 to S4. Good to see the AFM is pretty easily to swap also. Are the S5 manifolds just a better flowing design? I'm guessing the CPU isn't swapable? Here it is quoted from Mark:

Sorta Right...

The complete heavy duty suspension was found only on the

86-87 Sport
87-88 Turbo
88 GTU
88 Convertible

But parts of the heavy duty suspension also found on the

86-88 GXL
89-91 Turbo
89-91 convertible


The 89-90 GTUs used the same exact suspension as all the other 89-91 non turbo coupes. The GTUs only used the 89-91 Turbos wheels and brakes.

So why would they only use the heavy duty suspension on the S4 and just parts of it on other models?

Ice_Wolf

So, how is the clutch type LSD more predictable and are the CPU's swapable between the S4 and S5? Anything to back up the S4 drivetrain being stronger?

Ice_Wolf

Alright, so for the full list of differences:

Exterior:
Bumpers
Trim
Tailights
Mirrors
Wing
Rims
Gas tank

Suspension:
S4 had the "heavy duty" suspension

Engine:
Stronger rotor bearings
Higher compression rotors
Twin-scroll turbo
Electronically controlled wastegate
Manifolds
AFM
CPU

Drivetrain:
Transmission (S4 had stronger synchros)
LSD
Flywheel

Interior:
Better plastics
Seats
Door panels
Gauges
Idiot light setup
Logicon
Optional cargo cover

Icemark

Because the lock up was force proportionate, where as a Viscous LSD needs to see an amount of slippage for the fluid to harden

CPU's (body computers) are not interchangeable between series and the ECU's (engine computers) are also not interchangeable between series.
Because consumers were complaining that the Heavy duty suspension was too heavy duty. The S5 models are much more softer and isolated feeling when driving down the road (as that was the direction the market was going in the late 80's).

actually the S5 plastics are worse and tend to crack out more often... much cheaper construction, and the optional cargo cover was standard on some S5 models and of course optional as a dealer available option on any FC (regardless of series).

The dealer option S4 cargo cover is actually a much better design than the S5, as the S4 could be taken apart and folded in half in case you needed the extra space.

kleetuz

iTrader: (2)

s4 has less weight

7dust

iTrader: (14)

OH and S4's are hella ugly compared to an S5.

CyberPitz

D: I resent that and disagree, good sir!

adrock3217

Don't lie to yourself. You are secretly pricing the cost of a repaint AS WE TYPE.


And you know it.


I know it.


Let it be known!

Boost or Bust

iTrader: (1)

Another major difference is the OMP. In the S4 it is mechanical but in the S5 the Ecu controls the OMP. So even if do manage to plug in the s5 computer in an s4(you can't because they are different plugs) the car won't run properly because of the OMP. I don't even think an s4 can turn on with an s5 computer.

SpeedOfLife

iTrader: (16)

I'm really liking my S4 TII... although I always thought the argument was that the S5's had more durable interior and exterior trim pieces? rubberized vs hard brittle plastic.

Icemark

The only rubberized part was the radio/logicon surround and shifter surround. All the other plastics where the same hard ABS plastic found through out most cars.

The S5 coupes also had a much smaller arm rest glove box and no sport arm rest option.

SpeedOfLife

iTrader: (16)

I see. Well the only non-stock thing the PO of my '87 TII is they installed an S5 radio surround, so now I need the shift surround, I might modify the old S4 one to fit for the time being...

kleetuz

iTrader: (2)

square tail lights match the body lines on the s4

SpeedOfLife

iTrader: (16)

w00t

13b4me

All body lines are the same.

Ice_Wolf

Alright, so to revise the list:

Exterior:
Different front bumper
Different rear bumper
Different side mouldings
S5 had round tailights, S4 had square ones
S5 had rounder mirrors, S4 had square ones (both had option for aero type mirrors)
Wings were different between series, and depended on which model you had
Rims were different bweteen series, and depended on which model you had
S5 had 18.5 gallon tank, S4 had 16 gallon

Suspension:
S4 had the heavy duty suspension, and S5 just had parts of it

Engine:
S5 had a lighter rotating assembly (better for higher RPM power)
S4 had a heavier rotating assembly (better for lower RPM power)
S5 had stronger rotor bearings
S5 had higher compression rotors, which were lighter and slightly weaker
S5 had twin-scroll turbo
S5 had an electronically controlled wastegate
S5 had better flowing manifolds
S5 used the more efficient plunger-type AFM
S5 used a faster processing ECU
Mechanical OMP on S4, computer controlled on S5

Drivetrain:
S5 had a different 5th gearing with more ribs on the external case, and had weaker synchros than the S4
S5 had viscious type LSD, whereas S4 had clutch type (personal choice which is better)
S5 had a synchromesh reverse gear
S5 used a lighter flywheel

Interior:
S5 had rubberized radio/logicon surround (tend to crack more often)
S5 had rubberized shifter surround (tend to crack more often)
Seats
Door panels
Gauges
Idiot light setup and surround
Logicon
S5 had a standard cargo cover on some models, but the deal option cargo cover for the S4 was a better design
S5 had a smaller arm rest
S5 had a smaller glove box
S5 had no sport arm rest option

Wasn't the idiot light surround also rubberized on the S5? And what do you mean by smaller arm rest and no sport arm rest option?

SpeedOfLife

iTrader: (16)

but the S5's have round translucent tail light lenses vs the rectangular of the S4's.

Icemark

.. only on Turbo models. Some S4 non turbos didn't have the heavy duty suspension
No, the rubberized shifter and radio surrounds of the S5 models didn't crack more often, the rubberized coating reduced that. Some of the other interior parts cracked more often

, no, the 88 Turbo (as all 88 models did) used the same style idiot light surround that was used on the S5 models, and while the idiot lights looked the same between the 88 and the S5 models, they worked differently and had different icons
The only difference between the 87+ S4 and S5 logicon was the sticker with the icons
No all S5 coupes had a smaller arm rest glove box... the standard glove box was the same size, just Mazda deleted the flocked interior on the main glove box that the S4 mid and high level models had.
No the idiot light surround was the same for the 88 S4 and the later models and was not rubberized.

The Sport Arm rest was a $50 or so S4 option that was a triple height arm rest in the center console. This allowed you to rest your elbow easier without leaning.

Ice_Wolf

Yea Icemark, I'm basically speaking of the turbo differences here. Guess I'll revise my list.

Exterior:
Different front bumper
Different rear bumper
Different side moldings
S5 had round tailights, S4 had square ones
S5 models came standard with the rounder aero mirrors, The only the 88 GTU, 88 Convertible and 88 Turbo model had a version of the aero mirrors.
Wings were different between series, and depended on which model you had
Rims were different between series, and depended on which model you had
S5 had 18.5 gallon tank, S4 had 16 gallon

Suspension:
S4 had the heavy duty suspension, and S5 just had parts of it

Engine:
S5 had a lighter rotating assembly (better for higher RPM power)
S4 had a heavier rotating assembly (better for lower RPM power)
S5 had higher compression rotors, which were lighter and slightly weaker
S5 had twin-scroll turbo
S5 had an electronically controlled wastegate
S5 had better flowing manifolds
S5 used the more efficient plunger-type AFM
S5 used a faster processing ECU
Mechanical OMP on S4, computer controlled on S5

Drivetrain:
S5 had a different 5th gearing with more ribs on the external case, and had weaker synchros than the S4
S5 had viscious type LSD, whereas S4 had clutch type (personal choice which is better)
S5 had a synchromesh reverse gear
S5 used a lighter flywheel

Interior:
S5 had rubberized radio/logicon surround (cracked less often than the S4)
S5 had rubberized shifter surround (cracked less often than the S4)
Seats
S5 had some dash and trunk pieces liked to crack more often than the S4 pieces
Door panels
Gauges
88 and S5 models had the Visor'd idiot light surround.
88 and S5 models had the blacked out look idiot light setup. They looked simular but had different icons and wired differently
86-87 models had a different idiot light setup than the S5 models
Sticker on the logicon
S5 had a standard cargo cover on some models, The S4 models had the dealer option cargo cover which was a foldable design
S5 had a smaller arm rest glove box interior due to the mouse belts.
S5 did not have the flocked interior on the glove box, from the S4 GXL and Turbo II models
S5 had no sport arm rest option (triple height arm rest)

Alright, I think that should about do it. I can't really think of anything else.

<moderators note= I got tired of explaining the differences so I just edited the bigger flaws>